The present invention relates generally to machines for road paving operations and, more particularly, to assessing the quality of a paved road surface using Global Navigation Satellite Systems.
Methods of designing and paving/surfacing streets, highways and other such roadways, and the equipment used in such paving operations, are extremely well known. For example, in one such method, an asphalt mixture is spread on a properly graded and prepared surface and the mixture is then compacted using, for example, an asphalt compactor. The terms asphalt compactor, roller and roller machine are used interchangeably herein. One skilled in the art will recognize that there are many different types of paving/surfacing operations suitable for different circumstances.
One key assessment of finished roadways is the quality of ride that is experienced by a vehicle as it passes over the roadway. Profilographs, which are well-known in the art, are typically used after construction of a roadway is completed as one method of measuring ride quality. A profilograph is a measurement device that is passed over a roadway to detect the presence and severity of bumps and dips in order to generate a longitudinal profile of the roadway. FIG. 1 shows a prior art profilograph 100 useful for this purpose. Referring to that figure, profilograph 100 has a frame 102 which is, for example, a lightweight aluminum frame. Exemplary profilograph 100 has a length L of 25 feet. Frame 102 is supported above roadway 109 by wheel assemblies 101 and is adapted to be towed behind a vehicle in direction 110. Measurement wheel 108 is attached to arm 107 which, in turn, is attached to mounting box 104 mounted to frame 102 in a way that permits arm 107 and, hence, wheel 108, to move vertically to follow the contour of road 109 as the wheel passes over the road. Measurement wheel and/or arm 107 is connected to recording device 103 via cable 106 and flexible shaft 105. As wheel 108 moves up and down vertically, i.e. over bumps and into dips in a roadway as the profilograph is towed, cable 106 shortens and lengthens, respectively and flexible shaft 105 rotates in relationship to the rotation of wheel 108. Recording device 103 records the variations in the length of cable 106 as a function of the rotation of wheel 108 and compares the vertical position of wheel 108 to the known, fixed position of wheel assemblies 101. Since the number of rotations of wheel 108 are directly proportional to the distance traveled by the profilograph, recording device 103 can accurately record the relative position of wheel 108 with respect to the wheel assemblies 101 in order to determine any fast elevation changes within the length of the profilograph 100 that may function to degrade ride quality. These elevation changes experienced along roadway 109 can then be plotted as a function of the distance from a starting point of the profilograph in order to generate a longitudinal profile of that roadway. Recording device 103 may be an analog device with a physical pen connected to cable 106. In such a case, the pen moves proportionately with the change in length of cable 106 and records the dips and bumps on a roll of paper that is scrolled relative to the pen at a speed proportional to the rotational velocity of wheel 108. Alternatively, recording device 103 may be a digital computing device that records roadway profile information in digital memory. In either case, the result is a profile or graph of a roadway showing any fast elevation changes as a function of distance traveled which can effect the ride quality of a vehicle passing over that roadway.
Other variations on profilographs have also been used. For example, profilographs that are shorter in length have been developed that are useful at higher speeds than the profilograph of FIG. 1, which is limited to relatively slow speeds. Additionally, laser ranging devices have also been used in profilographs, herein referred to as laser profilographs. Laser profilographs typically consist of one or more laser devices attached to a vehicle. The laser is pointed at the roadway as the vehicle moves and one or more sensors measure, for example, the time the light energy emitted from the laser takes to travel from the laser device to the sensor, thus allowing a measurement of the distance from the laser to the ground. The longer the light energy takes to travel from the laser device, be reflected by the road and reach the sensor, the greater the distance above the ground the laser device/sensor are located. The speed of the vehicle is recorded while the distance measurements are taken and this information is transmitted to a computer, which records the information in order to create a profile of the roadway.